Electrostatic printing with stencils mounted on a drum



Sept. 26, 1967 M. A. SCHUELER 3,343,433

ELECTROSTATIC PRINTING WITH STENCILS MOUNTED ON A DRUM 4 Sheets-Sheet 1Filed March 15, 1965 nN W: H MIHIHHWIH wu ch IW l HIH .mIH

mum mm wn no MHUHmHH m INVENTOR- MARLIN A. SCHUELER E a [ff/lawATTORNEYS p 26, 1967 M. A. SCHUELER 3,343,483

ELECTROSTATIC PRINTING WITH STENCILS MOUNTED ON A DRUM Filed March 15,1965 4 SheetsSheet 2 (was? mnxaxmaxi-axmxmx 5 IE'IIEFLA l I I 1 131cm?Dim DXG-JIQIQIGL INVENTOR. MARLIN A. SCH UELER 'fw /rwmwo AT TORNEYSSept. 1967 M. A. SCHUELER 3,343,483

ELECTROSTATIC PRINTING WITH STENCILS MOUNTED ON A DRUM Filed March 15,1965 4 Sheets-Sheet I5 INVENTOR.

MARLIN A. SCHUELER ATTORNEYS p 26, 1967 M. A. SCHUELER 3,343,483

ELECTROSTATIC PRINTING WITH STENCILS MOUNTED ON A DRUM Filed March 15,1965 4 Sheets-Sheet 4 INVENTOR.

MRLEN A. SCHUELER BY 7 y m Y ATTORNEYS United States Patent ()fifice3,343,483 Patented Sept. 26, 1967 3,343,483 ELECTROSTATIC PRINTING WITHSTENCILS MOUNTED ON A DRUM Marlin A. Schueler, Danville, Calif.,assignor to Unimark Corporation, a corporation of California Filed Mar.15, 1965, Ser. No. 439,720 8 Claims. (Cl. 101-114) This inventionrelates to electrostatic printing generally along the lines described inUS. Patent No. 3,081,698, issued Mar. 19, 1963, to C. O. Childress et-al., in that a surface-dry powder is employed as the printing medium,and such powder is conducted across an air gap from a supply thereofonto the subject to be printed upon. The transfer of the powder iseffected by establishing an electrostatic field between the powder andthe said object.

One of the objects of this invention is the provision of improvedapparatus for printing by the above system, in which a substantiallyuniform air gap is maintained between the powder and the articleirrespective of variations in the size of the articles.

Another object of the invention is the provision of an improved printingsystem for printing on articles or material, and which system includesimproved conveyor means for carrying the articles.

An added object of the invention is the provision of improved means forsupporting the screen stencils that, in turn, support the powder to betransferred onto the articles or material to be imprinted.

A still further object is the provision of improved means fordistributing the powder onto the screen stencils that support the powderfor transfer onto the objects to be printed upon, and for moving asubstantially uniform :layer of said powder through the screen openingsfor said transfer thereof.

An additional object is the provision of improved means for successivelytransferring symbols, designs, etc. onto material or objects passingbelow the screen.

Another object is the provision of improved means and method for rapidlyand clearly electrostatically printing on objects of irregular shape andsize, such as potatoes, avocados, cucumbers, etc., by the system broadlydescribed in the aforesaid patent in that the printing medium is powderthat is transferred, electrostatically, across an air gap onto thearticles.

A further object is the provision of structure whereby multicolorelectrostatic printing is enabled.

Other objects and advantages will appear in the description anddrawings.

FIG. 1 is a side elevational view of apparatus illustrative of aprinting system embodying the present invention and the method.

FIG. 2 is a semi-diagrammatic top plan view of the apparatus of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view taken along line 3-3 ofFIG. 2 showing drive means.

FIG. 4 is an enlarged fragmentary side elevational view of the drum andassociated mechanism at the printing station.

FIG. 5 is a cross-sectional view generally as viewed from line 5-5 ofFIG. 4.

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5 withportions cut away for purposes of clarity.

FIG. 7 is an enlarged cross-sectional view taken along line 7-7 of FIG.4.

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7.

FIG. 9 is a fragmentary cross-sectional view taken along line 9-9 ofFIG. 8.

FIG. 10 is a fragmentary bottom plan view of part of the printing drumas seen from line 10-14 of FIG. 8.

FIG. 11 is a fragmentary side elevational view of the portion of themachine shown in FIG. 8 showing in broken lines interior parts in adifferent position from those shown in full line in FIG. 8.

FIG. 12 is a fragmentary cross-sectional view taken along line 12-12 ofFIG. 11.

FIG. 13 is a fragmentary cross-sectional view showing a modification ofpart of the printing drum, partly in elevation.

In detail, refer-ring to FIGS. 1, 2, the apparatus illustrated forcarrying out the invention comprises a feed hopper 1 or any othersuitable feed device, at one end of an endless, horizontally elongatedconveyor, generally designated 2. Articles or material to be imprintedare fed from the hopper or feeder 1 onto the feed end of conveyor 2,which may also be called the rear end of the apparatus, for beingcarried forwardly to and past the printing station generally designated3 to the discharge or forward end 4 of the apparatus where the printedarticles or material are discharged.

The use of the words rear, rearward, forward and forwardly are used withrespect to the direction of movement of the articles or conveyor 2, thelatter carrying the articles forwardly.

Conveyor 2 comprises a pair of endless chains 5 (FIGS. 4, 5), opposedlinks of which carry shafts 6 that respectively support adjacent pairsof rollers 7 between said chains for rotation of said rollers about therespective axes of said shafts.

The chains 5 extend over pairs of sprocket wheels 9, 10 (FIG. 1)respectively at the rear and forward ends of the apparatus, which pairsof wheels are carried by shafts supported for rotation in bearingscarried by frame 1.

The rear end portion 11 (FIG. 1) of conveyor 2 extends slantinglyupwardly from the feeder 1, the upper runs of said chains being slidablysupported on the upper edges of guide strips 12 (FIG. 5) that, in turn,are rigid with the frame 1 and are upwardly inclined in a forwarddirection from feeder 1 for slantingly supporting said portion 11.

The lower runs of conveyor 2 are similarly supported on the upper edgesof guide strips 13 (FIG. 5) that are also rigid on frame 1.

At the upper end of portion 11, the upper and lower runs of the chains 5respectively extend over rollers or sprocket wheels 14, 15 (FIG. 1) orany other suitable means and from said rollers or wheels the upper andlower runs of the chains 5 extend horizontally to and over the end pairof sprocket wheels 10.

The guide strips 12, 13 support the conveyor against sagging, and thisis articularly important with the upper run, inasmuch as it carries thearticles to be printed upon past and below the printing device at theprinting station 3.

The means for driving the chains and other portions of the apparatuscomprises a motor 18 (FIG. 1) in driving relation with a sprocket wheel19. Sprocket wheel 19 is connected with a sprocket wheel 20 by a chain21, said wheel 29 being secured on. a shaft 22 that, in turn, isrotatably supported at its ends in bearings 23 (FIG. 3) carried by frame1, said shaft extending transversely of the conveyor below the upper runof chains 5 at a point adjacent to the printing station 3.

The shaft 22 has a bevel gear 24 (FIG. 3) secured thereto in a positionbetween the opposed side frame members 25 of frame 1, and gear 24 is inmesh with a bevel gear 26 on a shaft 27 that extends parallel withconveyor 2 between said frame members 25. This shaft 27 is rotatablysupported at its ends in bearings carried by said frame members, andgear 26 is secured on one end of said shaft while a bevel gear 28 issecured on its opposite end. The gear 28 is in mesh with a bevel gear 29that is sewith the said chains through suitable gaps (not shown) in theguide tracks 11 for driving the chains.

The shafts 6 of rollers 7 are equally spaced along chains 5, and therollers themselves are the same, each being circular in cross-sectionalcontour and the central portions 34 (FIG. of each roller may becylindrical and of reduced diameter while the opposite end portions 35are of progressively increasing diameter from said central portion inopposite outward directions to provide surfaces that are slightlyconcave lengthwise of the rollers. These end portions commence at theiradjacent ends at said central portion, to be of slightly larger diameterthan the central portion.

By this arrangement'each adjacent pair of rollers will provide a cradlefor supporting a vegetable, such as a potato, avocado or other fruit orvegetables. The rollers shown are suitable for potatoes, each of whichcenters itself in the cradle formed by an adjacent pair of rollers, andthe rollers, being rotatable, facilitate such centering,

' and also facilitate proper printing on each article, as will bedescribed later.

The rollers 7 are spaced apart. and their diameters are such that anobject cradled orsupported by one pair will not contact the articlessupported by the adjacent pairs that include one of the rollers of saidone pair. Such articles are generally indicated at 73 (FIGS. 4, 5).

Frame 1 is provided with a pair of upwardly projecting posts 37 (FIGS.4, 7) that extend a substantial distance above the conveyor 2. Posts 37are in spaced opposed relation at opposite sides of the conveyor and arerigid with frame 1.

A horizontal shaft 39 is rotatably supported at its ends in hearingscarried by the posts 37 at their upper ends.

Two pairs of arms 40, 41 (FIGS. 4, 5, 7) are respectively supported atone of their ends on the opposite ends of shaft 39 (FIG. 4). These armsextend generally horizontally from shaft 39 (FIG. 1) in the direction ofmovement of the upper run of conveyor 2, and arms 40 may be called theinner arms, since they are adjacent to each other, while arms 41 are theouter arms, or the ones outside the arms 40.

Supported between the forward ends of arms 40, 41 is a polysidedprinting drum generally designated 42 (FIGS. 1, 4) which drum is 'atprinting station 3.

Before going into complete detail as to drum 42, it is sufficient atthis point to say that it comprises a pair of spaced opposed side plates43, 44 (FIGS. 5, 7) connected around their outer peripheral edges byflat plates 45 (FIG. 8) that carry the screens, as will be describedlater more in detail.

Sides plates 43, 44 of drum or wheel 42 are respectively centrallysecured on coaxial sleeves 46, 47 (FIG. 7) through which a horizontalshaft 48 extends, and outwardly of side plate 44 and sleeve 47 is atiming pulley 49, the hub of which is coaxial and rigid with sleeve 47.Shaft 48 also extends through the hub of pulley 49 and through anothersleeve 50 outwardly of and coaxial and rigid with said hub.

The bores of the sleeves 46, 47, 59 and the hub of pulley 49 aresubstantially greater in diameter than the outside diameter of shaft 48(FIG. 7). Thus the shaft 48 and the drum or wheel 42 are adapted to moverelatively in a direction transversely of said shaft. FIG. 7 shows space51 between the bores of said sleeves and shaft 48.

Ball bearings 54 (FIGS. 6, 7) respectively on sleeves 46, 50 supportsaid sleeves for rotation in the outer ends of arms 40, hence the drumor wheel 42 is rotatably supported in the outer ends of said arms 40.

The sleeves 46, 47, 50, and the hub of pulley 49 may,

Y 4 insofar as function is concerned, he considered as a hollow shaftthrough which the shaft 48 freely extends and on which hollow shaft thedrum or wheel 42 is supported for rotation therewith.

Referring back to FIGS. 3, 4, the shaft 22 that carries the sprocketwheel 20 and which shaft has a timing pulley 55 secured thereon at theside of the apparatus opposite to the side shown in FIG. 1 (FIG. 4) anda timing belt 56 connects pulley 55 with a timing pulley 57 on shaft 39.

Shaft 39 also has a timing pulley 58 thereon that is connected by atiming belt 59 with pulley 49 on sleeve 47 (FIG. 7) that is secured tothe printing wheel or drum 42. Since the latter as well as the hollowshaft comprising sleeves 46, 47, 50 and the hub of wheel 42 arerotatable as a unit in bearings 54, it is seen that the train of timingbelts and pulleys to the pulley 47 will elfect rotation of the wheel 42in timed relation to conveyor 2 upon actuation of motor 18.

The words timing belt, and timing pulley and the plural thereof, referto conventional belts and pulleys that are connected for movementtogether in substantially the same manner as sprocket chains andsprocket wheels.

Shaft 48 that extends through the sleeves forming the hollow shaft isrigidly secured at its opposite ends to the forward or outer ends ofouter arms 41 (FIG. 7) through which the outer ends of shaft 48 extend,said last mentioned outer ends being of reduced diameter to provideaxially outwardly facing shoulders against which the inner or opposedlyfacing surfaces of the outer ends ofarms 40 are clamped by nuts 62.

Radially outwardly projecting flanges 63, 64 respectively on sleeves 46,50 may function to space bearings 54 from side plate 43 of the printingdrum and from the pulley 49.

Carried by and rigid with side frame members 25 are upstanding members65 (FIG. 5) having opposedly extending arms 66 (FIG. 5), each of which,in turn, carries a resilient bumper 60 (FIG. 6) at their adjacent ends.These bumpers are adjacent to the outer ends of outer arms 41 andsupport said outer ends of arm 41 thereon.

Secured to the outer end of each arm 40 is a pair of laterally outwardlyprojecting, vertically spaced stop elements 67, 68, the elements 67being the upper stop elements and elements 68 being the lower ones, andthe elements of their pairs ext-end across the upper and lower edges orsides of the outer arms 41. Vertical adjusting screws 69 are threadedlysecured on the outer ends of arms 41 and project downwardly and upwardlyfrom the upper and lower sides of said arms for engagement with stopelements 67, 68 respectively for adjustahly limiting the degree of upand down movement of the outer ends of arms 41 relative to the outerends of arm 40.

By the foregoing construction it is seen that drum 42 and the outer endsof arms 40 will move upwardly from a lowermost position relative to theshaft 48, before the.

outer ends of arms 41v and shaft 48 move upwardly, but as soon as thelower screws 69 on the outer ends of arms 41 are engaged by lower stopmembers 68, the outer ends of arms 40, 41 will move upwardly together.

When arms 41 are in their lowermost position, the 7 upper adjustingscrews 69 on the outer ends of arms 41 will support the upper stopmembers 67 thereon and the outer ends of arm 41 will be supported onstationary resilient bumpers 60.

As has been explained, the side plates 43, 44 of drum 42 are connectedby stencil or screw supporting plates 45. These plates 45 are of thesame size and are flat and the outer peripheral edges of the side plates43, 44 are polygonal in outline so that the said flat screen or stencilcarrying plates 45 may be secured along two of their opposite edges fromend to end of each pair of opposed parallel straight outer peripheraledges of side plates 43, 44 and may be secured thereto by any suitablemeans such as screws 70. Said plates 45 and the screws thereon enclosethe space between the side plates 43, 44 and form the .peripheral outersides of the drum 42, the screen being described below.

Each plate 45 is formed with an aperture 71 (FIG. 13) and a flat stencilscreen 72 (FIGS. 8, 13) extends across the opening, being positioned atthe radially inwardly facing side of each aperture so that the thicknessof the plate 45 will be between the screen 72 and the article, such aspotato 73, to space the outer surface of the potato that is opposed tosaid screen from the screen, thereby providing a relatively uniform airgap between the screen and the potato.

Each screen 72 may be of woven nylon or any other suitable electricallychargeable material, and the openings of the area defining the design tobe printed on article or material 73 are of a uniform size for passingthe particles of the powder therethrough as described in the hereinabovementioned patent. The stencil screen 72 may also be formed in anysuitable manner, one being as described in said patent.

A printing mechanism 77 (FIG. 8) is disposed within the drum 42, whichmechanism, as an assembly, is carried by shaft 48. A supporting member78 for said printing mechanism, is keyed to said shaft 48 againstrotation relative to the latter.

A rotary brush generally designated 80 has a cover, preferably of mohairor the like, providing the short, radially outward bristles of suchbrush, and a horizontal shaft 82 rotatable at its ends in hearings onsupport 78 support the brush for rotation. Shaft 82 is parallel with theshaft 48, and the latter is parallel with the shaft supporting the drum42.

When the drum 42 is in its lowermost position with the upper stopmembers 67 supported on upper screws 69, the brush 80 will be out ofengagement with the inner surface of the outer side of the drum, or thelowermost screen 72, and in this position the brush is free from drivingengagement with a drive means of any kind.

Also carried by the supporting member or body 78 is a magazine or holder83 for the printing powder, which may be in loose powder form orcompressed into the form of a block or stick 84 extending generallyradially of the axis of brush 80 with one end frictionally engaging theouter surface of said brush over the area of the latter that is adaptedto wipe or brush across the openings in screen 72. This stick preferablyis located above the brush 80 and is of a texture or consistency wherebyadequate powder from the stick will abrade onto the bristles or outerperiphery of the brush to be carried by said bristles onto the screen 72when the bristles move downwardly to the screen and also said powder sodeposited on to the upper or inner surface of the screen will be movedthrough the screen openings upon rotation of the brush while inengagement with the screen, as will later be described more in detail.

The holder 83 for stick 84 is generally tubular with an open enddirected toward the brush 80 out of which the lower end of the stick 84extends into said engagement with the brush, and one or more weights 85may be slidably supported in the upper end of the holder 83 against theupper end of the stick to maintain the lower ends of said sticks againstthe brush under suitable uniform pressure under the gravitational forceof the weights.

Secured to brush 81) coaxial therewith is a ratchet wheel 86 (FIG. 8).As seen in FIG. 8, wheel 86 is rotatable counterclockwise, or in adirection opposite to the direction of rotation of drum 42, and a springleaf 87 secured to any stationary part of or attached to support 78engages the teeth of wheel 86 to prevent rotation of the latter andbrush 80 in the same direction of rotation as that of the drum.

One side of the member 78 is formed with a recess 89 (FIGS. 8, 9) intowhich a shaft 90 projects, and on the projecting end of said shaft andin said recess are a pair of bearings 93, 94. Bearing 93 supports oneend of a crank arm 95 while bearing 94 supports an arm 96 at a pointintermediate the ends of the latter for rotation of arms 95, 96 relativeto each other about the axis of shaft 90.

One side of arm 95 faces arm 96 (FIG. 8) and said side is relieved atthe surface so engaging arm 96 to provide a shoulder 97 adapted toengage an edge of arm 96 to form a stop to prevent the arms 95, 96 fromswinging relative to each other to a more acute angular relationshipthan is shown in FIG. 8.

A stop pin 98 stationary on the stationary supporting member or body 78is adapted to be engaged by the upper end portion of arm 96 above shaftto limit the counterclockwise rotation of arm 96 as seen in FIG. 8, anda spring 99 connected with said upper end of arm 96 and the body 78yieldably holds said upper end against said stop pin 98.

A spring 108 connects the portion of arm 96 below shaft 90 with the armto yieldably hold the arm 96 against the shoulder 97 on arm 95.

Pivotally mounted on the outer end of arm 95 by pivot 192 is a pawl 103having a tooth at one end that is yieldably held into engagement withthe teeth of ratchet wheel 86 by means of a spring 104 that connects anarm on the other end of the pawl with an arm 106 rigid with andprojecting from arm 95.

When the roller or brush 80 is in the position for printing, as seen inFIG. 8, the lower end of arm 96 is in what may be termed its rear andlowermost position directed substantially vertically, and can be movedonly forwardly or clockwise.

Rigid with the side plate 44 of drum 42 that is adjacent and opposed toarm 96 are a plurality of lugs 107 that are rigid with said side plateand equally spaced from the axis of the drum with one lug for eachscreen circumferentially spaced equal distances from each other. Thelower end of arm 96 is in the path of said lugs, and the latter arepositioned so as to engage the lower end of each arm at a point wheneach screen is substantially in printing position. As the drum is drivenclockwise in FIG. 8 substantially a distance at least equal to thedistance circumferentially of the drum of the printing area of thescreen, the brush 86 will be rotated counterclockwise due to theratchet-pawl engagement between ratchet wheel 86 and pawl 103, and atthe end of such movement the lower end of arm 96 will be'disengaged fromthe lug 197 that is in engagement therewith and the pawl 183 and arm 96will spring back to starting position until the next lug 197 in theannular row thereof engages the lower end of arm 96 and again rotatesthe brush 80.

An electrical DC. power source 168 (FIG. 1) of the desired voltage mayelectrically connect with the rollers of conveyor 2 at the printingstation and with the brush 80 or each screen 72 when the latter movespast the printing station to thereby establish an electrical potentialbetween the screen and the article, such as potato 73 when they are inthe position shown in FIG. 8, and the bristles of the roller 89 willmove the discrete powder particles through the screen openings and intothe electrostatic field in the air gap between the screen and eachpotato for conduction onto each potato in the pattern corresponding tothe pattern of the screen openings. Conductor 199 may extend from thevoltage source to the brush 89 or screen 72 and conductor 118 to therollers 7 through member 114, or any other suitable and conventionalcircuit may be provided to establish the desired electrical potential.

Also, referring to FIG. 2, an air jet or nozzle 111 may be supported byany suitable portion of the stationary frame that supports the operatingelements of the machine, in a position for blowing air against the outersides of the screens after each printing operation for cleaning theouter surfaces of the outer periphery of the printing drum and screensof any printing powder that may adhere thereto. Such source ofcompressed air is 7 indicated in FIG. 2 at 112 and the line leading tothe nozzle is indicated at 113.

After the articles have been carried beyond the printing station 3, theyare moved past any suitable valve actuated fixing device 115 forspraying a fixative onto the powder and article for fixing the powderonto each article. Obviously a conventional heater may be used insteadof a fixative, it being understood that either of these ways of fixingthe powder is conventional, and each may be valve actuated.

In operation (FIG. 2) articles 73 are deposited on adjacent pairs ofrollers 7 of the upper run of conveyor for automatic centering betweenor on each pair. The articles may be fed onto said upper run from hopper1, or in any other suitable manner.

From hopper 1 said articles are carried by the conveyor 2 for movementto and past the printing station 3 and below the printing drum 42.

When there is no material, or no article in a printing position belowthe drum 42, the latter is nevertheless rotating in synchronism with theconveyor 2, but the outer ends of arms 40 support the drum in itslowermost position, with the abrading and powder applying brush 82stationary and spaced above the printing screens or the walls formingthe outer periphery of the drum 42. 7 Upon material, or an article, onconveyor 2 moving toward a position below the drum 42, the outerperipheral wall of the drum, during rotation of the latter, will engagethe material or article, causing the drum to be elevated so that theradially inner surface of the screen will engage the abrading roller 80,and at the same time the lower end of arm 96 will move into the path oftravel of the lugs 107 to be engaged thereby. This engagement occurs atthe point just in advance of, or it may be at the point where thepattern of openings in screen 72 commence as the drum rotates, and whenthe screen is in spaced opposed relation to the material or article onthe conveyor 2.

Continued rotation of the drum 42 after the outer end of arm 96 isengaged by a lug 107 results in rotating the powder abrading anddistributing brush 80 relative to the inner surface of the screenthrough movement of arm 96 by lug 107 and consequent actuation of theratchet wheel 86 by pawl 103.

The lug or projection 107 will clear the lower end of arm 96 after eachprinting operation and the roller actuating mechanism including arm 96and pawl 103 will quickly be returned to starting position for anotheractuation of roller 80 by the next approaching lug or projection 107,but should there be no article or material on the conveyor in a positionfor printing the drum will automatically move downwardly and away fromthe roller 80 under the influence of gravity, and the lugs 107 will notengage the arm 96, hence there will be no rotation of the abradingroller 80.

The employment of the separately replaceable screens enables quickreplacement if for any reason one of the screens is not printingproperly due to the screen, or each screen may be formed for printingdifferent information, usually in the latter case the material to beprinted.

In FIG. 12 a modification of the powder feed is shown in which a holder117, similar to holder 83, is shown in which there is a plurality ofsticks or bodies 118 of compressed powder in a row, the said bodiesbeing separated by partitions 119 dividing the housing or container intoseparate compartments in side by side relation for separating thebodies. The latter are respectively supported in engagement withseparate brushes 120 rigid on a single shaft 121 corresponding to shaft82 in FIG. 8 and actuated in the same manner as described for roller 80,the shaft having a ratchet wheel 122 secured to one end thereof forengagement with pawl 103 when used in the arrangement described in FIG.8.

By the above structure, a multicolor printing may be 8 readilyperformed, each body of powder being a different color.

The employment of a compressed body of powder from which a uniformamount is abraded only when a printing operation is performed, enablesthe operator to reduce the amount of floating or surplus powder to anegligi-ble degree. Weights such as weights or any other suitable formof pressure are used in the housing or holder in FIG. 12, each of thebodies being urged into engagement with one of the brushes. Thus meansis employed for varying the pressure of the bodies against the rollersby increasing or decreasing the number of weights, so that more or lesspowder is abraded from each block, stick or body of powder.

In connection with the foregoing, it may be emphasized that thecharacter of the printing is to an appreciable degree dependent upon theuniformity of the amount of powder brushed through the openings in eachprinting screen.

I claim:

1. In an electrostatic printing machine, the combination comprising:

(a) a drum-like wheel supported for rotation about a horizontallydisposed axis, and having radially outwardly outer peripheral wallsthat, in turn, include an annular row of screens coaxial with said axis,each having radially inwardly and radially outwardly facing sidesrelative to said axis, and each formed with a plurality of openings in apredetermined pattern corresponding to the designs to be printed;

(b) a conveyor including article supporting means for supportingarticles to be printed upon for movement along a predetermined path oftravel projecting from said article supporting means and means foractuating said conveyor for moving said article supporting mean-s tomove the articles thereon along said path;

(c) wheel supporting means for supporting said wheel over said path at'apoint therealong for movement of one of said screens into opposedprinting relation to each of said articles when each article is closestto said wheel, and means connecting said conveyor with said'wheelrotating the latter to move screens to said opposed printing relationupon actuation of said conveyor;

(d) a supply of printing powder Within said wheel;

(e) powder distributing and moving means within said wheel between saidsupply and each screen when the latter is in printing relation to one ofsaid articles for depositing powder from said supply onto the radiallyinwardly facing side of said screen, and for moving the powder sodeposited through the openings in each screen to the radially outwardlyside of each screen;

(f) means for establishing an electrostatic field between the screen andarticle in said printing relation for conducting the powder movedthrough said openings onto the article opposed thereto upon any onescreen and article being moved to said printing relation;

(g) means on said wheel rigid therewith and around the plurality ofopenings in each screen projecting radially outwardly of each screenrelative to the axis of said wheel for engaging the outer surface of anarticle on said conveyor around the portion to be printed upon when ascreen is in said opposed printing relation to such article for spacingthe screen from said article.

2. The combination as defined in claim 1, including:

(h) said conveyor being a row of adjacent pairs of equally spacedrotatable rollers connected for movement along said path, each of saidrollers having generally conical end portions with their smallerdiameter ends adjacent to each other for supporting and automaticallycentering each article adjacent tion comprising:

(a) a carrier for supporting material to be printed upon past astationary printing station;

(b) a screen at said printing station formed with a plurality ofopenings in a predetermined pattern corresponding to the design to beprinted on said material;

(c) screen supporting means for supporting said screen in a positionopposed relative to material at said station adapted to be carriedtherepast by said carrier;

(d) said screen supporting means including a mechanism supporting saidscreen for movement toward and away from material on said carrier; and

(e) material engaging means connected with said screen movable therewithto a position for engagement with material on said carrier as it iscarried therepast and for actuating thereof by movement of said materialengaging means past said station for spacing said screen at said stationa substantially uniform distance for such material;

(f) means connected with said carrier for moving it and material thereonpast said printing station;

(g) powder depositing means for depositing printing powder on the sideof said screen opposite to said carrier for passage through the openingsin said screen and onto material in opposed relation to the latter atsaid printing station;

(h) means for establishing an electrostatic field between said screenand material at said station when said material is in said opposedrelation only;

(i) and means adjacent to said station supported for movement to aposition for engagement with said material on said carrier at saidstation during movement of the latter therepast actuatable by saidengagement and movement for moving powder on said screen through saidopenings and into said electrostatic field, said last mentioned meansbeing automatically movable to an inoperative position in the absence ofmaterial on said screen, whereby no powder will be deposited by saidpowder distributing means on said screen in the absence of a material atsaid station in a position to be printed upon.

4. In an electrostatic printing machine, the combination comprising:

(a) a carrier for supporting material to be printed upon past astationary printing station;

(b) a screen at said printing station formed With a plurality ofopenings in a predetermined pattern corresponding to the design to beprinted on said material;

(c) screen supporting means for supporting said screen in a positionopposed relative to material at said station adapted to be carriedtherepast by said carrier;

(d) said screen supporting means including a mechanism supporting saidscreen for movement toward and away from material on said carrier; and

(e) material engaging means connected with said screen movable therewithto a position for engagement with material on said carrier as it iscarried therepast and for actuating thereof by movement of said materialengaging means past said station for spacing said screen at said stationa substantially uniform distance for such material;

(if) means connected with said carrier for moving it and materialthereon past said printing station;

(g) powder depositing means for depositing printing powder on the sideof said screen opposite to said carrier for passing through the openingsin said screen and onto material in opposed relation to the latter atsaid printing station;

(h) a supply of printing powder spaced from said screen;

(i) movable powder-conducting means supported for movement from saidsupply of printing powder to said screen and operatively connected withsaid screen for conducting powder from said supply to said screen uponmovement of said screen under the influence of movement of said materialengaging means when said material engaging means is in engagement withmaterial on said carrier.

5. An electrostatic printing machine, comprising:

(a) a horizontally disposed, drum-like wheel supported for rotationabout a horizontal axis, and having an annular row of screens coaxialwith said axis defining outer peripheral walls of said wheel, eachscreen formed with a group of openings is a pattern corresponding to adesign to be printed, said screens having, radially inwardly andoutwardly facing sides, relative to said axis;

(b) a conveyor including a horizontally extending row of articlesuporting means for supporting thereon articles of different verticalthicknesses to be printed upon, whereby said articles will projectdifferent distances above said row of article supporting means, saidarticle supporting means being supported for movement longitudinally ofsaid row thereof and con-veyor actuating means connected with saidconveyor for so moving said article supporting means;

(c) wheel supporting means for supporting said wheel for rotation aboutits axis, and in a position over said row of article supporting meansfor moving said screen, in succession into opposed printing relation toarticles on said article supporting means at the point along said row ofarticle supporting means at which said screens are closest to articleson said article supporting means upon rotation of said wheel and uponactuation of said conveyor;

((1) wheel actuating means operably connected with said conveyoractuating means for simultaneously rotating said :wheel and foractuating said conveyor, for movement of the screens and articles onsaid article supporting means to said printing relation at said point;

(e) means for establishing an electrostatic field between said screensand articles on said article supporting means at said point forconducting printing powder moved through the group of openings in eachscreen onto an article on an article supporting means at said point;

(if) a powder supply within said wheel and powder distributing means fordepositing powder therefrom onto the radially facing side of each screenat said point and for moving the powder so deposited through the groupof openings in such screen and into said electrostatic field, duringrotation of said wheel and actuation of said conveyor;

(g) article engaging means on said wheel adjacent to each screen forengaging an article on article supporting means at said point forspacing such screen and article a substantially uniform distance fromeach other during said rotation of said wheel and actuation of saidconveyor;

(h) said wheel supporting means including means supporting said Wheelfor bodily movement different distances toward and away from saidarticle supporting means under the influence of articles engaged by said11 article engaging means at said point, according to said differentthicknesses of articles on said article supporting means for maintainingsubstantially uni form spacing between the screens and articles on saidprinting relation at said point.

6. In a printing machine as defined in claim (i) each of said screensbeing planar, and means for removably securing each of said screens tosaid wheel around the outer periphery thereof for selective replacementof said screens, and said screens, respectively, being tangential to acircle coaxial with the axis of said screen.

7. In a printing machine as defined in claim 5:

(i) means supporting said powder distributing means within said wheelfor bodily movement of said wheel relative thereto in a direction towardan article supporting means and out of engagement with said powderdistributing means, at said point, in the absence of an article on anarticle supporting means being in engagement with said article engagingmeans.

8. In a printing machine as defined in claim 7:

(j) said powder supply being a unitary body of compacted printing powderabradable upon movement of said powder distributing and moving meansthereof; and

(k) said powder distributing means being a rotary brush having itsradially outwardly facing surface in frictional engagement with saidbody;

12 (1) brush rotating means including meansrcspective- 1y on'said wheeland brush supported for movement into driving relation with each otherfor rotating said brush upon engagement of said article engaging meanswith an article on said article supporting means at said point, andmovable out of said engagement with each other in the absence of anarticle on such article supporting means at said point.

References Cited UNITED STATES PATENTS 1,167,004 1/1916 Magna 101-381,501,817 7/1924 Sevigne 101-40 2,432,202 12/1947 Mason 101-2272,473,729 6/ 1949 Salz 118-637 2,866,403 12/1958 Simmerman et al. 101-38X 2,950,671 8/1960 Allen et a1. 101-40 2,974,632 3/1961 Westervelt etal. 118-637 2,987,037 6/1961 Bolton 118-637 3,081,698 3/1963 Childresset al. 101-129 3,115,091 12/1963 Hakogi 101-40 X 3,198,116 8/1965Mikurak 101-40X 3,218,967 11/1965 Childress 101-114 3,218,968 11/1965Childress et a1 101-115 3,228,326 1/ 1966 Childress et al.

ROBERT E. PULFREY, Primary Examiner.

E. S. BURR, Assistant Examiner.

1. IN AN ELECTROSTATIC PRINTING MACHINE, THE COMBINATION COMPRISING: (A)A DRUM-LIKE WHEEL SUPPORTED FOR ROTATION ABOUT A HORIZONTALLY DISPOSEDAXIS, AND HAVING RADIALLY OUTWARDLY OUTER PERIPHERAL WALLS THAT, INTURN, INCLUDE AND ANNULAR ROW OF SCREENS COAXIAL WITH SAID AXIS, EACHHAVING RADIALLY INWARDLY AND RADIALLY OUTWARDLY FACING SIDES RELATIVE TOSAID AXIS, AND EACH FORMED WITH A PLURALITY OF OPENINGS IN APREDETERMINED PATTERN CORRESPONDING TO THE DESIGNS TO BE PRINTED; (B) ACONVEYOR INCLUDING ARTICLE SUPPORTING MEANS FOR SUPPORTING ARTICLES TOBE PRINTED UPON FOR MOVEMENT ALONG A PREDETERMINED PATH OF TRAVELPROJECTING FROM SAID ARTICLE SUPPORTING MEANS AND MEANS FOR ACTUATINGSAID CONVEYOR FOR MOVING SAID ARTICLE SUPPORTING MEANS TO MOVE THEARTICLES THEREON ALONG SAID PATH; (C) WHEEL SUPPORTING MEANS FORSUPPORTING SAID WHEEL OVER SAID PATH AT A POINT THEREALONG FOR MOVEMENTOF ONE OF SAID SCREENS INTO OPPOSED PRINTING RELATION TO EACH OF SAIDARTICLES WHEN EACH ARTICLE IS CLOSEST TO SAID WHEEL, AND MEANSCONNECTING SAID CONVEYOR WITH SAID WHEEL ROTATING THE LATTER TO MOVESCREENS TO SAID OPPOSED PRINTING RELATION UPON ACTUATION OF SAIDCONVEYOR; (D) A SUPPLY OF PRINTING POWDER WITHIN SAID WHEEL; (E) POWDERDISTRIBUTING AND MOVING MEANS WITHIN SAID WHEEL BETWEEN SAID SUPPLY ANDEACH SCREEN WHEN THE LATTER IS IN PRINTING RELATION TO ONE OF SAIDARTICLES FOR DEPOSITING POWDER FROM SAID SUPPLY ONTO THE RADIALLYINWARDLY FACING SIDE OF SAID SCREEN, AND FOR MOVING THE POWDER SODEPOSITED THROUGH THE OPENINGS IN EACH SCREEN TO THE RADIALLY OUTWARDLYSIDE OF EACH SCREEN; (F) MEANS FOR ESTABLISHING AN ELECTROSTATIC FIELDBETWEEN THE SCREEN AND ARTICLE IN SAID PRINTING RELATION FOR CONDUCTINGTHE POWDER MOVED THROUGH SAID OPENINGS ONTO THE ARTICLE OPPOSED THERETOUPON ANY ONE SCREEN AND ARTICLE BEING MOVED TO SAID PRINTING RELATION;(G) MEANS ON SAID WHEEL RIGID THEREWITH AND AROUND THE PLURALITY OFOPENINGS IN EACH SCREEN PROJECTING RADIALLY OUTWARDLY OF EACH SCREENRELATIVE TO THE AXIS OF SAID WHEEL FOR ENGAGING THE OUTER SURFACE OF ANARTICLE ON SAID CONVEYOR AROUND THE PORTION TO BE PRINTED UPON WHEN ASCREEN IS IN SAID OPPOSED PRINTING RELATION TO SUCH ARTICLE FOR SPACINGTHE SCREEN FROM SAID ARTICLE.